In recent years, a product functioning as a camera or a video camera has been rapidly made small enough to be put in a pocket and carried or to be optionally mounted on other electronic devices such as a mobile phone. Because of the compact size of these optical equipments, the need has been increasing year by year to lighten and reduce the size of components constituting those equipments.
In general, a light-shielding material used for a camera or the like has been primarily a metal. But, in view of lightening and reducing the size of the component and achieving cost reduction, the switching to a plastic material such as a resin film was desired. As a resin film used for the light-shielding component, for example, JP-2008-138068A (Patent Document 1) discloses that a resin obtained by dispersing carbon blacks in a polyester film will provide a film with high light-shielding effect. JP-H04-009802 (Patent Document 2) discloses a process for coating both faces of a synthetic resin film with a thermosetting resin composition containing carbon blacks to provide a light-shielding film.
However, recent tendency to adopt a production process using reflow soldering to increase the productivity demands that the resin used for a lens unit of a camera withstand the reflow soldering process. The light-shielding film as exemplified above, because having a low glass transition temperature (Tg) as a component and having no reflow soldering resistance, cannot be produced in the production process including the reflow soldering process. For this reason, the productivity has not been improved.
In addition, the light-shielding material is required to have good molding processability. Furthermore, when used for a component for precision equipment, the material is required to have electrical conductivity, as needed, to reduce troubles due to static electricity.